The long range objective of this project is to provide evidence that chromium is an essential trace element required by man. Chromium, in the form of glucose tolerance factor (GTF), is required for a normal insulin response in insulin -- sensitive tissues. Dietary supplementation with crude GTF has been demonstrated to improve glucose tolerance in elderly subjects with previously impaired glucose tolerance. Serum cholesterol and triglycerides levels are also reduced, as a result of this dietary supplementation. Long term studies in pre-diabetics and potential diabetics as judged by family history are in progress. The crude GTF supplements have normalized the elevated glucose and insulin levels in some subjects who have a genetic predisposition to diabetes. It is possible that early recognition of prediabetes coupled with GTF supplementation of the diet may alter the usual progression of prediabetes to overt diabetes. Evidence is accumulating that the American diet does not provide enough chromium or the chromium containing complex, GTF. Thus, chromium deficiency does exist in this country.